Public health efforts in preventing HIV and related diseases with injection drug users require clear understandings of the risk environment of drug consumption. One important aspect of the risk environment is drug supply. Specifically, the supply of heroin into the United States is changing dramatically: Over the past twenty years, heroin prices have decreased nationwide to record levels as purity has increased. This has occurred during the same time period as the number of heroin source regions has been reduced from 4 to 2. Heroin use is associated with significant social and medical problems. HIV and other blood-borne infections, e.g., hepatitis C, are still major concerns, but there is also rising concern about non-HIV heroin related medical consequences, e.g., heroin related overdose (HOD), soft tissue and other bacterial infections (BSTI), including abscess, cellulitis, necrotizing fasciitis and various clostridial infections, and endocarditis. The two US sources of heroin produce chemically distinct forms which maybe perceived/used differently. The two major heroin morphologies, Black tar heroin (BTH) and powdered heroin (PH) have preliminary associations with specific diseases. BTH is suggestively associated with soft tissue infections, while PH is ecologically correlated with HIV. These two forms have distinct geographic markets with BTH predominating in the western US and PH in the eastern US. Notably, preliminary research has shown significant ecological correlation between HIV prevalence among heroin injectors in western and eastern US cities and regional differences in the distribution of BTH and PH. Very little research has been done that analyzes the distinctive health problems associated with the different types of heroin and relates these differences to patterns of use. The purpose of this study is to illuminate the medical consequences particular to the two major types of heroin commonly found in the United States and relate them to changes in availability, price, purity and differing use patterns for these drugs. The specific objectives of this research project are: 1. To examine the trends in heroin related medical outcomes, e.g., HOD, BSTI, in up to 29 US metropolitan areas (MSAs), between 1990-2006, by changes in local heroin price and purity. 2. To examine the associations between the distribution of specific types of heroin (i.e., BTH and PH) and heroin related outcomes, e.g., HIV, HOD, and BSTI, in 20 US MSAs, controlling for confounding variables. 3. To assess the behaviors and belief systems of heroin users related to their use of specific types of heroin, in two cities; each with an exemplar heroin type. The Heroin Price, Purity and Outcomes (HPPO) study proposes a mixed methods approach. Specific Aims 1 and 2 will be achieved by combining governmental databases on heroin economic data with multiple national databases on medical outcomes, analyzed using advanced statistical techniques. Specific Aim 3 will involve two forms of qualitative inquiry: ethnographic assessment and in-depth qualitative interviews.